Thursday, May 10, 2012

How to View Stereo 3D Content

Stereoscopic 3D imaging provides depth to pictures by simulating the different views seen by each eye. While the concept is as old as photography, it has gained an unprecedented amount of support in the last two years from the entertainment and consumer electronics industry. A growing number of major movies are being filmed in 3D, major video games are being released in 3D, all major TV and monitor manufacturers are making 3D TVs and Nintendo has released a 3D version of their hand held game console. All of these are potential viewing devices for 3D images.

All stereoscopic 3D images, whether still or video, consist of two separate views in which elements are positioned differently depending on how deep they are in the scene. Viewing a stereoscopic 3D image requires a method to allow each eye to see only one of the two images. Here are the most common methods for viewing stereoscopic content:

Parallel View – Parallel view consists of placing the left and right images side-by-side on a monitor or printed card. While some users are able to fuse the two images into a single 3D image on their own, most require a viewer to help focus each eye on the correct image. One of the simplest and most effective is the Loreo Pixi viewer which consists of two prisms mounted in a folding cardboard glasses frame. Using the Loreo viewer,  any computer monitor can be used to display 3D content.

The Loreo Pixi 3D Viewer
Red/Cyan Anaglyph – An anaglyph image applies a red cast to one view and a cyan cast to the other. Glasses with red and cyan lenses filter the views for each eye. This is one of the easiest and cheapest methods because the images can be displayed on any device and cardboard red/cyan glasses can be purchased in bulk for about $.50. However, the quality is poor. The method distorts the color of the image and there is frequently ghosting because the filters in the glasses do not match the display color. 

Anaglyph image of a bird in flight.
Passive Sequenced – The 3D movies currently shown at theaters use the passive sequenced method where the left and right images are projected one at a time in rapid sequence through filters polarized at opposing angles. The viewer wears glasses with polarized lenses to filter the images to each eye. This viewing method is also used with some consumer level 3D projectors.

Passive Interlaced – The passive interlaced method requires building the polarized filters into a TV monitor in strips. The right and left images are interlaced into the strips and the viewer wears polarized glasses to filter the images to each eye. This method is being used by some high end 3D TVs, but it adds significant cost to the production of the TV. As the costs come down, this may become the preferred technology for 3D in the living room because the glasses are inexpensive and do not require charging.

Toshiba Laptop with Active Shutter Glasses
Active Shutter Sequenced – Most of the 3D TVs that are in the stores currently use the active shutter sequenced method. The right and left images are shown in rapid sequence and the user wears a pair of glasses with LCD shutters which turn on and off in sync with the screen refresh on the TV monitor. This is the least expensive technology right now for the home because it does not require significant changes or additional costs for the monitor. The disadvantage, particularly in households with children, is the need for keeping the batteries in the glasses charged and the replacement costs if the glasses get lost or broken.
The Nintendo 3DS uses a parallax barrier to show 3D content.

Parallax Barrier – The Nintendo 3DS hand held gaming console, the display on the Fuji 3D camera and a number of recently announced 3D laptop computers have parallax barrier screens. With this method, the left and right images are interlaced onto an LCD screen. A second LCD screen layer creates a series of lines which keep each eye from seeing the images intended for the other eye. This approach is autostereoscopic which means that it works without any type of 3D glasses. However, the user has to be at a particular distance from the screen and at a particular angle to experience the 3D effect which limits its application to small, single-user devices.

Lenticular – Lenticular printing is not really a stereoscopic display method but instead mimics the effect of stereoscopic viewing. For lenticular printing, typically 12 to 24 images are interlaced into a single print which is laminated onto a special lens to allow the viewer to see different views as the image is rotated. To create a lenticular print from the left and right views of a stereoscopic 3D image, special software must be used to create the intermediate views.

Although there are many ways to view 3D content, I usually post images as a 3D stereo pair and a red/cyan anaglyph. This makes them accessible to readers with the least expensive viewing tools. 

How do you prefer to watch 3D content?

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